Quantum conductance oscillations in metal/molecule/metal switches at room temperature

We apply pressure-modulated conductance microscopy to metal/molecule/metal switches. Apart from pressure-induced conductance peaks that indicate nanoscale conducting pathways, we also observe dips and oscillations for devices with conductance between 1 and 2 conductance quantum. The conductance oscillations arise from interfering electron waves along one or two quantum conductance channels between two partially transmitting electrode surfaces at room temperature, underscoring these devices' potential as coherent, atomic-scale switches.     

Emulsion polymerization of hydrophobia monomers

Emulsion polymerization is the most important industrial polymerization process for manufacturing water based polymers. The heterogeneous nature of the process requires the diffusion of monomers from the emulsified droplets, through the aqueous medium, into the polymer particles where the polymerization takes place. Adequate solubility of the monomer is necessary for the diffusion process to occur effectively. Consequently, very hydrophobic monomers cannot be readily incorporated by emulsion polymerization. The use of a catalytic level of cyclodextrin allows the use of very hydrophobic monomers in emulsion polymerization.^[1] The mechanism of the process is believed to involve a catalytic cycle in which cyclodextrin acts as a “Phase Transport Catalyst”, continuously complexing and solubilizing the hydrophobic monomers and releasing them to the polymer particles. The kinetics and thermodynamics are favorable for the reaction to proceed.     

On the error term in an asymptotic formula for the symmetric square -function

Recently Wu proved that for all primes ,

where runs over all normalized newforms of weight 2 and level . Here we show that can be replaced by .

     

Characterization of crosstalk of a TDM FBG sensor array using a laser source

The crosstalk characteristics of a time-division multiplexing fiber Bragg grating sensor array that uses a laser source are examined. The system performance is found to be limited by the extinction ratio of the input optical pulse modulation and can be improved significantly by properly modulating the laser wavelength.     

Pricing/inventory decisions and profit shares in a non-integrated marketing channel for a single-period product

We consider the situation in which the manufacturer of a single-period product first sets the unit wholesale price and then the retailer responds with an order size. We present mostly analytical results on the effects of the problem's environmental parameters (such as shortage cost and demand uncertainty) on the optimal decisions (ie, the unit wholesale price and retailer's order size) and on the expected profits of the manufacturer and of the retailer. Some of these effects are counter-intuitive and/or contradict related results published recently for similar models. The most important finding is that demand uncertainty is always harmful to the manufacturer but is very often beneficial to the retailer. This means that when the manufacturer can set the wholesale price, the manufacturer should be much more supportive (or even aggressive) than previously advised towards activities such as market surveys and ‘Quick Response’ that reduce the retailer's market uncertainty; in contrast, the retailer need not be as enthusiastic about these activities.     

氮化钒的选态双色可见紫外共振增强光电离和脉冲场光电子研究 (cited: 4)

对气态氮化钒(VN)分子在光子总能量为56900～59020 cm^-13∏0, v'=0)的单转动态, 然后再被紫外激光电离．这样的双色激光模式可以测量电子态、振动态和转动态都被选择和解析的氮化钒阳离子VN⁺(X²△; v⁺=0, 1, 2)光谱． 通过对转动解析的PFI-PE光谱模拟分析, 确定J⁺=3/2为基态离子态的最低转动能级, 从而确认VN⁺的基态电子态为²△_3/2．通过对VN+(PFI-PE)光谱的分析得到如下物理量的精确数值：VN⁺(X²△_3/2)的绝热电离能为IE(VN)=56909.5±0.8 cm^-1(7.05588±0.00010 eV),振动常数ω_e⁺=1068.0±0.8 cm^-1,反常振动常数ω_e⁺χ_e⁺=5.8±0.8 cm^-1;VN⁺(X²△_3/2)的转动常数B_e⁺=0.6563±0.0005 cm^-1,α_e⁺=0.0069±0.0004 cm^-1,平衡键长为1.529 ?;VN⁺(X²△_5/2)的转动常数B_e⁺=0.6578±0.0028 cm^-1,α_e⁺=0.0085±0.0028 cm^-1,平衡键长为1.527 ?;X²△_5/2,3/2自旋轨道耦合常数A=153.3±0.8 cm^-1     

Synthesis of substituted 10,11-dihydro-5H-dibenz[b,f]azepines; key synthons in syntheses of pharmaceutically active compounds

Substituted 10,11-dihydro-5H-dibenz[b,f]azepines are key synthons in the syntheses of a number of pharmaceutically active compounds such as imipramine, chlorimipramine, and desimipramine analogues. A facile synthesis of substituted 10,11-dihydro-5H-dibenz[b,f]azepines is described, starting out from com mercially available 2-bromotoluenes or 2-nitrotoluenes. Initial α-bromination with N-bromosuccinimide and subsequent reaction with triethylphosphite afforded the corresponding benzyl phosphonic ester deriva tives. After reaction with benzaldehyde derivatives, the expected Horner-Emmons reaction products were obtained. Hydrogenation gave the amino derivatives which were transformed into the corresponding formamides. Under Goldberg conditions [1], the final ring closing step was performed to give the substituted 10,11-dihydro-5H-dibenz[b,f]azepines in 46–75% yield.     

Space-charge effects on multipactor on a dielectric

Analyzes the effects of space charge shielding on the steady state of a multipactor discharge on a dielectric. Analytic methods are used to obtain an exact function for the potential in the discharge, assuming a Maxwellian distribution of emitted electrons. An equation for the amount of power deposited on the dielectric by the multipactoring electrons, for a given saturation level, is given. A simple method for obtaining the saturation level, for a given material, is obtained     

Production of neutron-rich isotopes in fission of uranium induced by neutrons of 20 MeV average energy

In the context of a parameter study conducted by several laboratories for future European radioactive beam facilities based on fast-neutron induced fission, in particular for the SPIRAL-II project at GANIL, we have measured the yields of neutron-rich isotopes in the mass range of 88 to 144. These nuclei were obtained as fission products of natural uranium bombarded by neutrons of 20 MeV average energy emitted by a thick carbon target irradiated by 50 MeV deuterons. Yields have been measured using on-line mass separation with the ion-guide method. Compared with proton-induced fission at 25 MeV the magnitude of cross-sections, except for the symmetric region, is similar. Z-distributions of isobars have the same width, 0.7 charge units, but their maxima are shifted by about 0.8 charge units, favouring production of the neutron-richer isobars. Our data allow calculations of absolute cross-sections for fission of natural uranium induced by neutrons of about 20 MeV. Received: 10 July 2000 / Accepted: 27 October 2000